Although the inspectors were satisfied with the way complaints were investigated by the independent procurator fiscal service, they believed procedures tended to vary too much from force to force.

There should be a national code of practice dealing with the recording and and investigating of police complaints

Graham Power, Assistant Inspector of Constabulary

They identified the recording of complaints as an area which could be reviewed and cited the example of Grampian Police, where records of all complaints, even those settled amicably, were kept.

The inspectors said other forces did not include those statistics and so appeared to have fewer complaints.

Assistant Inspector of Constabulary, Graham Power, who was one of those involved in the compiling of the report, said the fact that different forces collected statistics in different ways meant that it was hard for the public and police authorities to come to a view about the performance of complaint investigations.

He added: "There should be a national code of practice dealing with the recording and and investigating of police complaints.

"These should be available to everyone, In this day and age, there ought to be information on the internet describing the rights of complainers and individual police officers."

Public confidence

The report has called for full audio and video recording of custody areas in police stations in the hope of cutting the number of complaints by those arrested.

And the inspectors said the role of the fiscal service should be easier to understand so that the public can have greater confidence in the complaints procedure.

Mr Power said that any major change in the police complaints procedure could take a long time.

He said: "What we're recommending are things which can be done now to make the present system stronger."

Independent body

Later this year, ministers will outline their own review of how complaints against the police should be dealt with.

The Scottish Human Rights Centre said this must provide for a fully independent investigating body as the only way to improve public confidence.

Mr Power said very few countries succeeded in delivering complete independence in complaints investigation, adding that most systems involved an element of oversight.

He said he believed that while there was no room for complacency, there was evidence that public confidence in the police was high.